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Comments on The Possibility of Knowledge
label for it than ‘problem of sources’). It is thus a new type of obstacle – obtaining at a
new level 0 – that is to be distinguished from the obstacles to be dealt with on level 2,
which are supposed to be obstacles to the utility of the means proposed on level 1. This
distinction between two types of obstacles would seem to be fairly obvious. Cassam,
however, fails to draw it, and we shall see that this failure helps to make his examples
look more uniform than they are.
Given that the obstacle on which HPsap ‘depends’ is a lack of means, it does
seem sensible to give a means response, as prescribed by Cassam’s schema. The means
of acquiring geometrical knowledge (the specific kind of synthetic a priori knowledge in
question) that Kant himself proposes is that of ‘construction in pure intuition’ (12). Kant
then goes on to identify as an obstacle to the utility of this means the fact that any
particular construction in pure intuition is singular, while geometrical propositions are
general (what Cassam calls the ‘problem of universality’ (14)). This is again in line with
Cassam’s schema in so far as we have here an obstacle to be removed on level 2. I’m
not sure, however, how ‘intuitive and pre-existing’ this obstacle really was for Kant. I
admit I do not know, but I would imagine that the ‘problem of universality’ only
occurred to him while pondering the mechanics of his means. In my view, if there is
anything like an intuitive and pre-existing obstacle playing a role in connection with
HPsap, it is the absence of means, i. e. the level 0 obstacle. In any event, I would guess
that it was this obstacle rather than the problem of universality that drove Kant to ask
HPsap.
Having removed the ‘problem of universality’ on level 2 (according to Cassam,
roughly by proposing that ‘it is the fact that construction is a rule-governed activity that
makes it possible for geometry to discern “the universal in the particular”’ (15)), Kant
moves on to level 3, where he gives a type B explanation by identifying ‘the fact that
space itself is an “a priori intuition”’ (18) as an enabling condition for construction in
pure intuition to generate geometrical knowledge. This once again fits Cassam’s
schema: Kant discusses an enabling condition that must be fulfilled if the means
proposed on level 1 is to generate the relevant knowledge. A question that can be raised,
however – and that Cassam indeed himself raises (cf. 20f.) – is what distinguishes this
level 3 response (this explanation of the power of construction in pure intuition to
generate geometrical knowledge in terms of the ideality of space) from the obstacle
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